Magic mushroom ingredient takes the fight out of aggressive fish
A psychedelic compound found in magic mushrooms appears to have an unexpected effect: calming highly aggressive fish. Researchers discovered that low doses of psilocybin significantly reduced aggressive attacks in mangrove rivulus fish without disrupting their normal social interactions. The findings suggest psilocybin may selectively calm escalating aggression rather than simply suppressing all behavior.
Key points
- Researchers in Canada found a low dose of psilocybin reduced aggressive attacks in mangrove rivulus fish.
- Treated fish showed fewer high-energy swimming bursts but kept lower-energy social displays.
- The team stressed the fish findings are not evidence of a human aggression treatment.
A brief, low dose of psilocybin reduced aggressive behavior in a naturally combative fish species, according to a study published in Frontiers in Behavioral Neuroscience. Researchers in Canada studied the amphibious mangrove rivulus fish (Kryptolebias marmoratus), which is known for aggressive responses when it meets another member of its species.
The team exposed fish to dissolved psilocybin for 20 minutes, then returned them to a tank with the same fish they had encountered the day before. Treated fish moved less and showed fewer aggressive swimming bursts than untreated fish.
How the experiment worked
The researchers used three genetically distinct laboratory-bred lines of fish. One group received psilocybin, another supplied the fish used to provoke social interactions, and a third helped measure how much psilocybin entered and accumulated in the animals' bodies.
Fish were first placed in a tank with another fish, separated by a fiberglass mesh barrier and an opaque cover, to set a baseline. The mesh allowed sight and smell but prevented physical contact. The next day, after 20 minutes of exposure to dissolved psilocybin, the same fish were observed again.
Psilocybin's calming effect appears to selectively reduce energetically costly, escalated behaviors while lower-energy social display behaviors remained largely unchanged
— Dayna Forsyth
What the researchers said
First author Dayna Forsyth, a research associate and former MSc student at Acadia University in Nova Scotia, said the study shows a low dose "significantly reduces activity and aggressive attack behavior" in the fish. Senior author Dr. Suzie Currie, a biologist at The University of British Columbia, said the findings provide the first evidence that psilocybin can selectively reduce escalated aggression in a vertebrate model without suppressing social interaction.
The team said psilocybin did not suppress every behavior: less physically demanding social displays remained largely unchanged. They cautioned that the results should not be read as evidence of a treatment for aggression in humans, and that only single doses and short exposure periods were tested.
